NWS Forecast Discussion
791
FXUS61 KCTP 281832
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
232 PM EDT Mon Apr 28 2025
.SYNOPSIS...
* Abundant sunshine, light winds, and mild temperatures for the
rest of this afternoon afternoon as a ridge of high pressure
drifts into Eastern PA.
* Warmer temperatures and moderate humidity returns for Tuesday
with numerous severe thunderstorms possible during the
afternoon and evening hours across mainly the northwest half
of the Commonwealth.
* Dry conditions prevail on Wednesday with next chances of
showers and thunderstorms Thursday afternoon through Friday
night.
&&
.NEAR TERM /THROUGH TONIGHT/...
A spectacular afternoon of almost cloud-free skies, but this
time (compared to Sunday) with light and variable winds in close
proximity to a ridge of high pressure over the Susquehanna
Valley.
Temps are nicely approaching their fcst highs in the upper 60s
to around 70F across the Northern Mtns and Laurel Highlands and
lower 70s elsewhere.
Fire concerns for the rest of today will be mitigated somewhat
by lighter winds today compared to yesterday along with recent
rainfall and green-up across southeastern Pennsylvania. As a
result, we`ve opted for no fire weather headlines this
afternoon.
Dry conditions with clear to partly cloudy skies continue into
tonight. A freshening southerly breeze and some increase in
strato cu clouds late will keep temperatures +10 to +20F warmer
by daybreak Tuesday compared to this morning.
Although cloud cover increases early Tuesday morning ahead of
an approaching upper-level trough tracking north of the area,
the entire region should stay rain-free into late Tuesday
morning/Tuesday afternoon before convection develops. More on
that below.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
An upper-level trough will push through the Great Lakes Tuesday
afternoon and bring a warm front/cold front progression through
the Commonwealth on Tuesday afternoon. This warm front is
expected to lift north of central Pennsylvania Tuesday morning,
allowing for much of the area to have some residence time in the
warm sector. This is expected to allow for warmer temperatures,
especially across western Pennsylvania where there is higher
confidence on the warm sector pushing north/east of the region.
Despite these warmer temperatures, cloud cover is expected to
limit instability across the western half of the forecast area;
however, increasingly diffluent upper level westerly flow and
ample shear/veering wind with height, beneath the right entrance
region of a mid/upper-level jet will lead to a notable
potential for severe weather with a high shear-low to moderate
CAPE environment during the afternoon and evening hours Tuesday.
Current storm mode favors multicell with some supercells likely
as hodographs take on a broad loop across the NW half of the CWA
by late Tuesday afternoon with 0-1KM EHI values from 2-3.5 M2/S2
across the Central and NW Mtns between 20Z Tue-00Z Wed. Main
threats at this time for severe weather will be damaging winds
in mini bow echoes within short line segments considering
strong, westerly 0-3 KM bulk shear of 40-45 KTS, and large hail,
especially across northwest PA. Given the potential for some
"right movers" creating significantly better storm relative
inflow and lowered pressure/LCLs beneath the strong updrafts,
there is risk for a few isolated tornadoes across the NW 1/3 or
so of Pennsylvania, especially from 22Z-00Z when LCL heights
will be lowering and storms interact with llvl outflow
boundaries from the initial convection.
SPC continues to highlight nearly the exact same part of the
state with an Enhanced Risk of SVR TSRA (Level 3 out of 5),
which happens about 6 times per year on average across
Pennsylvania.
Be sure to Have multiple ways to receive warnings and stay
weather aware Tuesday afternoon and evening as the likely
severe weather event evolves.
Storms will continue moving eastward late Tuesday
afternoon/evening; however, less instability will be in place
and shear becomes less favorable, thus severe threat becomes
more limited across the Lower Susquehanna Valley. Precipitation
exits quickly and becomes more upslope/lake- enhanced rain
showers in the wake of the cold front Tuesday night into early
Wednesday morning. Storm total rainfall amounts will be
generally less than 0.25" southeast of the I-99/I-81 corridor
and perhaps exceeding 1" in parts of northwest PA that receive
multiple rounds of storms.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The cold front becomes quasi-stationary to the south of the
MD Line early Wednesday night then pivots northward as a warm
front across western PA on Thursday as a sfc low tracks from
near Chicago into Lower MI by 02/00Z. Expect shower activity to
ramp up particularly in the western/northwestern portions of
the CWA through Thursday night near the intersection of the
advancing warm front and increasing moisture transport and
theta-e advection via relatively strong SSW 850mb LLJ and IVT.
Thursday night looks very mild in CPA for the first night of May
2025 with min temps 55-65F or +15 to +25 degrees above climo.
Scattered convection is likely to accompany the trailing cold
front on Friday, followed by another potential round of showers
Friday night into Saturday associated with the parent 500mb
trough/cool temps aloft rotating through the region. There is a
broad model consensus in a cooling trend Friday night into the
first weekend of May with 24hr min/maxT deltas running 5 to 10
degrees lower vs. the previous night/day. That said, frost risk
appears to be confined to the northern tier AM Sunday where the
growing season is not active.
High confidence in a much nicer end to the first weekend of May
as high pressure builds over the area into early next week.
Expect milder temperatures and pleasant, rain-free conditions
Sunday and Monday with highs moderating into the 65-75F range.
&&
.AVIATION /19Z MONDAY THROUGH SATURDAY/...
Little material change for the 18Z TAF cycle.
Earlier 15Z update introduced several hours of marginal LLWS
late tonight and early Tuesday at all airfields as the south-
southwesterly flow (above a mainly decoupled near surface
layer with a light south wind) freshens to 25 to 30 kts in a
layer between about 12-20 kft AGL.
High pressure across the region will (100% confidence) provide
light and variable to light south winds and clear skies through
about 29/06Z, followed by bkn-ovc high end MVFR to low end VFR
strato cu clouds.
A dual layer of clouds (expanding cu field, topped by cirrus)
will move into western Pennsylvania ahead of
showers/thunderstorms Tuesday afternoon; however, ceilings will
remain primarily above 20,000ft AGL.
Tue...PM showers and possibly a few thunderstorms with
restrictions possible. Brief gusty winds across W PA.
Wed...A few lingering showers across primarily SW PA.
Thu...Showers/t-storms return areawide, restrictions possible.
Fri...Showers with restrictions possible.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert/Banghoff
LONG TERM...Steinbugl
AVIATION...Lambert/NPB
NWS CTP Office Area Forecast Discussion
